Gas compressors are used for many items in the consumer market (to inflate basketballs, toys and tires) and in the industrial market (to compress gas for transport, for powering pneumatic tools and for distributing natural gas from the well head to the user).
The efficiency of prior art commercial gas compressors is poor primarily because practicalities require that the gas be compressed rapidly. Rapid compression makes it nearly impossible to dissipate the heat of compression during the compression process. This inherent heating during the compression process (herein “C-heat”) demands up to 100% more physical work from the prime mover than if the same process was done with complete and immediate “C-heat” removal. Typically the prime mover is an internal combustion engine or an electric motor. A rapid compression process with little or no C-heat removal is called an adiabatic compression. Most state of the art compressors operate with adiabatic or semi-adiabatic compression cycles. The energy or work lost due to C-heat increases as the final target pressure for the compressor increases.
The work potential of the isothermally compressed gas is roughly equivalent to the work required to compress the gas. However, most compressed gas is stored in an uninsulated pressure vessel and the time between the compression of the gas and the use of the gas makes retention of the heat in the gas impractical. Therefore, this 50-100% additional work to overcome the C-heat while compressing the gas is lost or wasted. Compression performed while immediately removing all of the C-heat is called isothermal compression. If isothermal compression can be achieved, the energy required to compress gas to a given pressure could theoretically be cut nearly in half. Stated otherwise, twice the amount of compressed gas could be produced for the same cost in energy or dollars. Historically isothermal compression has been impractical or impossible to achieve because the C-heat removal from the compressed gas requires too much time and/or additional energy for practical use.
One prior art references discusses a compressor with rapid isothermal compression. U.S. Pat. No. 892,772 to Taylor, patented in 1908, discloses a hydraulic air compressor which utilizes a falling column of water infused with millions of tiny spherical bubbles. When the column of water falls from a particular height, the bubbles in the water are compressed. Taylor used a 70 foot differential head pressure (about 21 meters) which creates roughly 30 PSI differential pressure to drive the compression process. Taylor used a 290 foot (about 88 meters) tall tail race to create and maintain approximately 128 psi (pounds per square inch) pressure to drive 5000-6000 horsepower isothermal compressors.
U.S. patent Ser. No. 14/280,780, filed May 19, 2014, (incorporated herein by reference thereto), U.S. Patent Application Publication No. 20150023807 (published Jan. 22, 2015) to Cherry et al discloses a centrifugal compressor that compresses gas in capillaries leading to a radially distant annular container space. Centrifugal force acts on gas bubbles entrained between liquid slugs moving radially outward (distally) through the capillary compression tubes which may be radial, tangential or continuously curved. Compressed gas is collected in an annular pressurized gas separation and storage chamber, whereupon it is harvested for industrial use. At the input side, a gas-liquid emulsion is fed to the capillary compression tubes by an inboard emulsification device. The emulsification device may include a vortex generator, an ejector or a venturi injector, all feeding the gas-liquid mixture into the inboard ports of the capillaries. The capillaries are formed in a series of discs, coaxially stacked with outer disc ends open to the annular disc space.
U.S. Pat. No. 6,276,140 to Keller discloses a device to generate energy through a turbine engine. The Keller device also uses falling water fed through a funnel shaped vertical tube or tunnel in order to compress air bubbles in the falling water. The waterfall drop in Keller was between 30-100 meters. Typical diameters at the top of the Keller funnel tube are approximately 2-7 meters and, at the bottom, the funnel outlet region is typically 0.7-2.0 meters.
U.S. Pat. No. 1,144,865 to Rees discloses a rotary pump, condenser and compressor. The Rees '865 rotary pump compressor utilizes large cavities having highly curved shaped walls and the cavities are not radial with respect to the rotating container.
U.S. Patent Application Publication No. 2011/0030359 to Fong generally discusses a centrifugal separator. U.S. Patent Application Publication No. 2011/0115223 to Stahlkopf also discusses centrifugal separators. Neither Fong '359 or Stahlkopf '223 discuss a centrifugal compressor which compresses bubbles in water or a liquid in an isothermal manner to extract the compressed air or gas.
U.S. Pat. No. 1,769,260 to Hughes discloses a centrifugal pump and condenser that uses capillary tubes to compress gas bubbles. However the manner in which Hughes creates a bubble train results in much longer and larger bubbles—with correspondingly greater bubble buoyancy—such that it is very difficult to force the bubbles towards the distal end of the compression tube. Hughes' shroud is a trough that collects water as it leaves the capillary chambers. The trough fills with water trapped due to centrifugal force at a depth determined by the inward facing flanges. Water which passes over these flanges is drained to the inside wall of a stationary cylindrical casing. The radially outboard ends of the capillary chambers extend radially beyond the internal diameter of the inwardly facing flanges creating a gas seal.
Hughes' shroud design has no significant pressure differential. Although Hughes' shroud acts as a seal by throwing the gas-liquid mixture at the radially remote inboard walls, the shroud design does not act as a rectifying agent to force unidirectional distal flow of entrained bubbles. Hughes's shroud design also does not provide a pressurized gas storage housing and a gas/liquid separation chamber. Hughes also does not disclose a method of recovering the kinetic energy imparted to the water by the impeller, therefore the gains of isothermal compression would be wasted on the energy imparted to the water.